'Squash' printed from http://nrich.maths.org/

In the game of squash, players gain "points" by winning
"rallies". If the "server" wins a rally, he or she wins a point;
otherwise the service changes hands with no points gained.

Normally the game is won by the first player to reach 9 points
-- typically by 2 or more points. But if the score reaches 8-8 then
the person due to receive serve can call "9" (in which case the
first to reach 9 wins) or call "10" (in which case the first to
reach 10 wins).

I'm playing a game against Ivana Slogovitch, the Russian squash
champion. I estimate that my chance of winning any particular rally
against her, regardless of whether I serve or not, is p. The score
gets to 8-8 and I am due to receive serve. Should I call "9" or
"10"?